1. Field of the Invention
The present invention relates to a pixel circuit and an organic light emitting display using the same, and more particularly, to a pixel circuit and an organic light emitting display using the same which can decrease a crosstalk due to a leakage current in an off-region of a pixel switching device to an undetectable level (or an invisible level), and compensate for variations in threshold voltages within itself to provide for uniform brightness.
2. Discussion of Related Art
Recently, as electric, electronic and semiconductor technologies have been developed, much research is being conducted for an improved flat panel display that can be employed in electronic devices such as monitors, televisions, portable terminals, etc. As a flat panel display, an organic light emitting display has advantages of high brightness, high emission efficiency, high definition, wide view angle, etc.
FIG. 1 is a schematic view of a conventional organic light emitting display 100. In FIG. 1, the organic light emitting display 100 is an active matrix type organic light emitting display.
Referring to FIG. 1, the organic light emitting display 100 includes a scan driver 110 adapted to supply a scan signal to a display panel 130 through a plurality of scan lines S1, S2, . . . , Sn (112); a data driver 120 adapted to transmit a data signal to the display panel 130 through a plurality of data lines D1, D2, D3, . . . , Dm (122); and a plurality of organic light emitting devices 144 adapted to display an image corresponding to the data signal. The display panel 130 includes a plurality of pixel circuits 132 to control the plurality of organic light emitting devices 144. An organic light emitting device 144 can represent a color such as white, red, green or blue with a predetermined brightness corresponding to the scan and data signals transmitted to a corresponding pixel circuit 132.
The display panel 130 is formed on a thin film transistor (TFT) array using a semiconductor process. In FIG. 1, the pixel circuit 132 includes a switching transistor M1, a storage capacitor C, and a driving transistor M2. The switching transistor M1 samples data. The storage capacitor C is programmed with the data. The driving transistor M2 is operated as a voltage source.
However, in the conventional organic light emitting display 100, there is a limit on how uniform the TFT array can be fabricated by a laser annealing process. Because of this limitation, the driving transistors M2 of the respective pixel circuits 132 may have different characteristics from each other, and distances between a power line supplying pixel voltage VDD and the respective pixel circuits 132 are also different from each other, so that a predetermined voltage difference (i.e., a voltage drop) arises in the pixel voltage VDD applied to each pixel circuit 132. To solve this problem, there have been proposed various circuits to compensate a voltage drop and a threshold voltage of the driving transistor in a pixel circuit.
Further, in the conventional organic light emitting display 100, as shown in FIG. 1, a switching transistor M1 of a pixel circuit 132 is connected between the data line Dm and a gate of the driving transistor M2. Therefore, an image data is applied to the gate of the driving transistor M2 through the switching transistor M1. In this case, in the pixel circuit 132 of the conventional organic light emitting display 100, a voltage applied to the gate of the driving transistor M2 varies due to a leakage current or an off-region current of the switching transistor M1. Thus, in a conventional organic light emitting display, a crosstalk arises between adjacent pixels due to a leakage current or a off-region current in a switching transistor.